Plot Elements are small scale, central ideas that can be used to pull a cast together and keeps them together. Each Character retains his or her individuality by dealing with and exploring the theme differently, but due to the common group that they all /have/ experienced this, it allows them to never be short of experiences to explore together. Not to mention it allow a nearly constant source of drama. For better or worse, with popularity and romance aside, they are all teens, and they need one another.
Now, you're probably wondering how a series of characters created by various people could possibly share a theme. Easy-it might have something to do with their background, where they all have a common origin story or defining moment. It could be their parents all died, or maybe they share the same immediate environment. For a small group of characters, the theme may be discovering the strength of their friendship; for kids from the same neighborhood, the theme may be about civic pride and how by improving the life of one person, the community prospers as a result. A Plot Element is a good way to find a central reason for a small story, you just have to try.
Disenfranchised
This theme deals with teen on the outside of society, outside the accepted norms of life. It might be their quest to make a place for themselves in society, it might be about surviving self-destructive behavior or surrendering to it, or it might be about how being the non-conformist isn't the negative society pretends it to be. This might be a moment when a character uses her disenfranchisement to her benefit, thereby validating her views on society or by proving society wrong about her. Again, it can be a negative thing if the character believes the worst of society and is proven right.
Family
Family…that wonderful, slippery eel you can never fully grasp and hold. And, it bites sometimes. Man-oh-man does it bite. Themes involving family might involve things like: "You never choose your family," "Blood is thicker than water," "Mom and Dad don't get me," and "They never listen." Familial themes might be about discovering the strength of a parent's love, familial obligations directing one's life, or how the lessons of the parents influence the child.
Fun
Not so much a theme as a reason to get together with friends, gorge on junk food, play videogames, and occasionally trash on the peon of the week. Fun simply means the teens are typical and well-adjusted, life is a hoot, and nothing is so serious that it stops being enjoyable. This was placed as a theme so that no rule-nazi could say "Hey! It doesn't say you can do that in the game!" It does now, and in case there are any arguments, fun covers zany, crazy, whacky, bonkers, wild, and anything else of a madcap nature.
Gender
Gender is not giggling at words like "Regina," "titmouse," and "balls." It does mean getting strength from the exploration of sex. (Stop giggling!) What does it mean to be a woman? What does it mean to be a man? And if you don't think it's important to teen identity, take a look at Emo and rave-kids who bend their gender (again with the giggling?) in defiance of social norms, goth-boys who wear make-up, or folks going to Rocky Horror in drag.
Gender can be a fluid thing to teens exploring their identities, and it can be a personal theme. It can also be a societal theme for gender-exclusive cultures like the fierce Amazons or their uppity cousins, the sororities. Frats count, too, as do male-dominated sports. Exploring those themes might include succeeding in a trial despite some opposition to you for your gender. Y'know, stuff like, "You can't do math, you're a girl!" or "You can't wear high heels, it clashes with your penis."
Growth
You see it all the time, from the teens trying to adjust and catch-up to their changing world to teens looking to be treated like adults. Or, growth can refer to your evolving maturity (or serious lack thereof). This theme deals with the accelerated growth all teens must endure in that all-too short transition from kid to adult (which always seems all-too-long at the time). In the span of six years, the world changes, and your body becomes some new enigma that constantly messes with your head. People don't seem to know how to treat you, either. They tell you to grow up, yet they won't give you the privileges that go with it. It's even worse among adults who suddenly think they have to protect you. With this theme, you could do something adult-like and prove wiser than your years, or if you frustrate an adult by doing something supremely juvenile.
Identity
Face it, you go from learning everything you know from Mom and Dad to suddenly realizing you want to be anyone but Mom and Dad. For this theme to work, you might need to figure out who your parents are and how they act. After that, identity is exploring what kind of person you'd like to become and whether it's a good fit or not. Sure, you'd love to be a rocker god or the latest hawtness on the Hollywood Red Carpet, but maybe it's in you to be the tech-savvy bookworm or the dark and dour mistress of the night.
Identity is more than just finding the true you, it's finding and being happy with what you find. It can also mean trying to change something in your character you perceive as a negative quality.
Image
Ah, image, the thing that makes people unhappy for being too skinny or too fat or too whatever. It also strikes the beautiful people by attacking their self-confidence with perceived flaws like a slightly crooked nose, a beauty mark, or some other trivial nonsense. Image is all about admiring society's ideal man or woman or idolizing a specific individual who personifies that ideal. It's about disliking one's self or maybe just studying a personal flaw too closely. Study a specific brushstroke on a painting and you fail to appreciate the painting itself.
This theme deals with accepting the imperfections in ourselves or in others, or perhaps it's about working to change them.
Religion
Religion is tricky in that "Watch out, that ravenous cougar has a landmine strapped to his back!" kind of way. Religion as a theme can run in any number of directions. It can be about a specific faith, or it can be a positive exploration of faith through the acceptance of life.
Romance
Romance is almost as bad as religion, and it can be just as rewarding. The theme might revolve around unrequited love, or once it's answered, holding on to the object of one's desire. Of course, you can turn that around 180 degrees, cue the creepy music and the pet-rabbit-in-the-pot routine, and voila instant stalker and obsession story-arc. And face it, any teen character with mega Charisma or the Attractive feat is stalker bait. Well technically that isn't romance, but romance can be one-sided.
Sexuality
Even more than romance, teens have to deal with their increasing sexuality, and that poses more challenges for some than it does for others, especially for teens with a growing awareness of bisexuality or homosexuality.
The reactions they receive or exhibit might run from tentative acceptance, to attempts to "save" them from their "choice," to outright hostility. What happens to the openly lesbian character if she encounters a homophobic one? How does a teen deal with his own uncertain sexuality upon encountering another who is completely out? Is the character responsible for representing "his community" as a gay teen? Is a heroine a lesbian but still in the closet?
There is no right or wrong answer to these questions because it's all opinion. Even the gay community itself is divided on subjects like outing closeted gays or whether bisexuality "truly" exists. This theme and the questions it explores are many and diverse.
Spirituality
Spirituality and religion aren't mutually exclusive. You can be spiritual but not follow the tenets of a particular religion, and you can be religious without being spiritual. Spirituality is an emotional exploration of self in relation to something greater (Gaia, God, Allah, Yahweh, the universal spirit, the breathing cosmos, or what have you). It implies an attempt to connect with a greater plane of existence than the material one. It could be the girl trying to find balance in her life or the boy trying to reach beyond the words of his religion's holy texts. Regardless, the theme of spirituality is an attempt to foster a relationship with some universal force.